New insights were presented through systematic experiments for the coalescing behaviors of oil-droplet swarms on the surface of inclined plates and the intensifying mechanism of oil-water separation with plate pack.It is found that when arriving at the inclined plate,the oil-droplets clinging to the surface of plate will not form a continuous oil film as usually regarded,but a rugged surface consisting of dispersed droplets.The subsequent oil droplets will not coalesce directly into this layer.Large oil droplets will roll upwards on the surface of droplets-layer and then leave the inclined plate,while small oil droplets will be retained in some hollow place of the rugged surface and finally coalesced and separated from water after some time period,during which four consecutive stages took place:film drainage,coalescence and growth,forming a random channel,and leaving the plate.The principle of plate pack intensifying the separation of small oil droplets comes from three aspects:shortening the ascending-time that oil droplets arrive at the plate;providing the rugged surface composed by dispersed droplets so that the small oil droplets can find suitable places to stay and complete the coalescence process;offering sufficient coalescence area for small oil droplets.This principle explains the experimental results well for the separation of small size oil droplets.To some extent,the increase of the plate pack length leads to an increased coalescence area,while the decrease of the inclined angle of plate will benefit to the coalescence of oil droplets,and both helps improve the separation efficiency.
